This invention relates to restitution instruments for measuring and evaluating picture plates. In particular this invention relates to an instrument for measuring and evaluating picture plates, e.g., photographs, photograms, transparencies, diapositives, and means for positioning such picture plate in the instrument, for graphical restitution, e.g. terrestrial photogrammetry, aereotriangulation, stereo restitution, etc.
By the use of the term "picture plate" it is generally meant to include any image or likeness of an object, person, or scene producted on a flat surface, especially by painting, drawing, or photography, and particularly includes photographs, photograms, transparencies and diapositives.
Devices for positioning picture plates for measurement and evaluation in restitution instruments are available which use a frame to hold the picture plate, e.g. U.S. Pat. No. 3,687,547. The frame is supported by a flat base plate and has two reference surfaces forming a right angle. A geared driving rack engages each of the reference surfaces by a pair of rollers. The rack is driven by a step motor through drive gear. This positioning device is constructed to permit rotation of the frame as well as linear movement. The geared racks pivot about the drive gear and remain perpendicular to the reference surfaces. At the area comprising the points of intersection of the center lines of the geared racks an optical observation system is rigidly mounted for observing given points on the picture plate after the stage has been moved into position with the aid of the step motors.
Since the rotational movements of the stage are not recorded, this positioning device suffers from positioning errors, the magnitude of which is a function of the angle of rotation and the diameter of the drive gears.
An object of this invention is to provide a restitution instrument for the evaluation and measurement of picture plates, including photographs, photograms, transparencies and diapositives, which has increased accuracy and stability when compared with known restitution instruments, at relatively low production costs.